Compression member for structures



F. E. VON EMPERGER. COMPRESSION MEMBER'FOR STRUCTURES.

APPLICATION FILED JUNE 17 1912 PatentedApr. 11, 1922.

4 SHEETS'SHEET 1.

ll l'l HIM-1L4).

' Attorney- F. E. VON EMPERGER. COMPRESSION MEMBER FOR STRUCTURES.

APPLICATION FILED man. 1912.

Patented Apr. 11, "1922.

. 4 SHEETS-SHEE]: 2.

9 I I f mwwgw FLE. VON EMPERGER- COMPRESSION MEMBER FOR STRUCTURES.APPLICATION FILED 1uua1'1. 1912.

1,412,096. E Pateiited Apr. 11, 1922 4 SHEETS-SHEET 3.

f/Lw W I Attorney F. E. VON EMPERGER.

COMPRESSION MEMBER FOR STRUCTURES.

APPLICATIQN FILED JUNE 1 7, I912 Patented Apr. 11, 1922.

6 6 Z 9 5 Z d O H 4 7 d U 2 n w o I ventor Attorney.

renting,

FRITZ EDLER VON EMPERG-ER,- OF VIENNA, AUSTRIA COMPRESSION MEMBER Eonsrnnornnns.

(GRANTED UNDER THE PROVISIONS on THE ACT or MARCH 3, 1921, 41 STAT.YI..," 1313.

To all whom it may concern:

Be it known that I, FRITZ EDLER VON EM- PnRoER, a sub ect of the Emperorof Austria,

and residing at Dominikanerbastei l, Vienna I, Austria, engineer, haveinvented certain new and useful Improvements in C0mpreS-. 51011Membersfor Structures, of which the following is a specification.

This invention relates to cast iron compression members for. structuresand has for its purpose considerably to increase the compressivestrength of such members by preprecedes buckling. According to theinvention, the members are constructed. by surrounding the cast ironcompression mem her, after having been brought into its position in'thestructure, with a Wrought iron hooping, arranged at a given distancetherefrom, and of sufficient tensile strength as to resist the radialstrains produced by the tendency of the cast iron member to bulge,

and by filling the interspace With a mate rial adapted to be impressedby the said strains and to transmit them to the hooping. The materialused for this purpose is con crete. Of course, girders Whose compressionflange is reinforced in' the manner referred to, fall within the scopeof the invention.

In the annexed drawings, which form a part of this specification, Figs.1 and 2. illustrate in sectional elevation and sectional )lan resectivel a com ressionmember In said figures, thenumerall denotescastn'on tube surrounded by .an envelope of hooped concrete Q'denotingthe helical windings 31 the longitudinal *reinforcing Thiscompressionmember for whatever purpose it may be applied, yieldstheefi'ect that although cast iron is a brittle and inelastic material,the member as a Whole.

formed as described of a 'castiron core em: bedded in hoopedconcrete,'possesses elastic properties and 'under compression behavesin. a manner which cannot be obtained with a material of high elasticlimit, such as mild steel. "Giving to this property aimore extendedsphere of use is securedfor cast iron and similar inexpensive materialsof the ,rind hereinbefore j mentioned, enabling these materials to beused in Works for Which they would previously have been deernedinsufficiently reliable. i 1

in a cheap ay, the bulging Which and 2.

The spacing of the straps or windings of the hooping depends broadlyonthe manner in which the member is stressed,- but the above mentioned'static effect is obtained when the said sp'acing -is approximatelyequal to the thicknessfiof the concrete envelope measured fromrthecastironc'core to the transverse reinforcement.- The thick bar ,7 of castiron of circularcross section Specification of Letters Patent. -Iag1itd-11; 1922 1 Application filed June 17, 1912. Serial No. 704,102. i I

'70 in which the core consists of'asolid for example, instead of thetube of l i Fig. at illustrates 'an adaptation of 1 the compressionmember to an 1 arch, which"may have a crown joint. Fig. 61s a crosssection on A Aof Fig. 4 and Fi 5 a corresponding sectional elevation.The-section on the line B+Bof Fig; s qcmay have any of the three formsillustrated'in Figs. 7, 8 and 9. As will be seen in these figures, threecompression members I, II and III of the above described type arearranged 3.Cl]2t(3611t to each otherat the abutment of the arch and areboundtogether by means of the concrete and if neces? sary also by meansof connecting irons. As these three compression members rise towards thecrown oftliearch, the middle member H is displaced above"-the plane of Imight also converge? towardsthej crovvn of,

of each tube having its ownhoo'ping the hoopingmay-be common, tofthethreefcast iron coresas shownin -Figssfiandf9; "iFig.

1.0illustrates afurther eXampleofan arched V bridge w-itli' three (oronly 'two) joints,;-Fig.

1r slio ing'fthe-cross section at fthe'position the position It 'Will beseenthat the -cast iron cores' are combined close to the.

joints into af single tube branching; into two tubes of semi-circularcross section, -as shown in F i'g. l1 thedistance apart of Which'tubes"gradually increases to the-maximum shown in thecross 'sect on'on D l).7 The hoopmg 12; the crossise'c'tionatf thefposi t-ion DD, and Fig.2thecrossfsection at- 90. V the other two. These compression'members ofthe two tubes is always common to both and when their distance apart islarge as in Fig. 12 cross reinforcing bars 8 between the tubes may beprovided. The gradual divergingof the cast iron cores in this case hasthe purpose of keeping the line of pressure inside the ellipse ofinertia of the reinforced. cross section. V

In the example illustrated in Figs. 11 and 12 the spacing of thetransverse reinforcement 2 of the concrete envelope may be equal to orsmaller than the least thickness of the concrete envelope measured fromthe cast iron core to the transverse reinforcement.

In Fig. 13 is illustrated a bridge girder of which the cross section onthe line FF may be as shown in Figs. 14 or 15. The compression flange ofthis girder as shown in Fig. la consists of a solid cast iron bar of Tcross section embedded in hooped concrete, and in Fig. 15 of threerectangular cast iron tubes, the central one of which is of elon gateddownwardly extending cross section.

The three tubes are embedded in a cement envelope and have a commonhooping. The hooping 2 also is reinforced by longitudinal bars 9, andtransverse reinforcing bars 8 are provided between the tubes. 7

The strengthening of hooped compression members by means of cores ofhigh compressive strength, as hereinbefore described, is not to beconfounded with theknown procedure of dressing cast iron columns withfire clay or even with cement concrete, as is done in the case of smokefines and the like, as this procedure merely yields a material of thesame strength as concrete and serving as a protection to the reinforcedconcrete against chemical and heating effects. The reasons why materialsof such high compressive strength as cast iron have not been used alonein the making of long compression members, consists among others in thatit is only possible to manufacture comparatively short members in asingle piece and that the uniting of several parts into a long member,apart from the danger of buckling, is attended with a loss in thetransmission of the stress from one member to the other, and this incombination with the unreliability of such built up members, renders theadoption of long built up members diflicult or impossible. If thereforestructural members of considerable length such as pillars, columns,arches and thelike are to be made out of such inaterials, a reliablemeans of connection of the .or abutting surfaces.

parts is necessary. The sources of loss just referred to WlllIlOW beexamined.

These losses arise in the first place owing to the unavoidableinequalities at the joints This circumstance, which cannot be obviatedeven by the most careful workmanship, has for result that the stressbecomes concentrated at particular places and the shearing forcesthereby created tend to split the whole member into vertical strips.Inthis manner a local failingmay take place long before the actualcompressive strength of the material has been fully developed.

Attempts have been made to overcome this drawback by carefullymachining, fitting and polishing the joint faces, but the futility ofsuch a procedure, is now generally recognized and a solution of thedifficulty is sought in the provision of cushions or the like forensuring uniform transmission of stress, for example cushions of sheetmetal or lead, or tar. The advantage of the better transmission of thestress is however impaired by the unavoidable softness of thecushionwhichbecomes plastic even at moderate pressures and has atendency to run out of the joints so that the aforesaid splitting intovertical pieces takes place and is even accelerated. The drawback,caused by this reduction in strength depends upon the thickness of thejoint, but when this latter is to fulfill its function, it must havecertain minimum dimensions. The effect of the cushioningsubstancebecomes the more prom inent the greater the difference in strengthbetween the two constituents so that in the case of cast iron cores nosubstantial economy or advantage is obtained. Thesame is also true ofcompression members-containing an assemblage of cast iron tubes. In thiscasealso a non-uniform transmission of stress is-the" cause ofunreliability such that without exceptional precautions the building upof compression members of several parts is not permissible.

The compression members according to this invention are adapted to beused with either single pieces of the cast iron or with pieces which areto be assembled into a longer member. The invention has therefore alsofor object the application of less hard cushioning material of the typeabove referred to at the abutting faces of the different componentmembers or core pieces in order to obtain a uniformtransmission of thethrust from one member to another. As this cushioning material isalsoembedded in the hooped concrete, it is prevented from being forced awayfrom its place of working, and also a splitting'of the structure invertical direction is obviated. Even if such a splitting should be givenit would not be injurious sincethe unity of the cross section is notimpaired. It would moreover be of advantage to arrange a strongertransverse reinforcement at these oint positions andto increase thenumber of longitudinal bars, to avoid the danger of buckling. Severalexani-ples of such compression members are illustrated. V

In Figs. 16 and 17, 1 denotes the core tubes which are only a fractionof the length of the compression member being made. so that a numberofsuch. tubes must prevented the con- I crete envelope from beingsqueezed out from between the jointing faces, its full effectiveness isensured up to the fullbreaking load-of the compression member. Anypossible forcing out of the cushioning material into thehol-low of thetubes can be prevented by means 'ofa short overlap of the latter at theinternal periphery. In the case illustrated flanges ll are also'providedat the joints which 13' near the joints, and in. addition ,the numberof-longitudinal barsis increased by the provision of additional bars lfor the purpose of diminishing thedanger of buckling, which in columnsforexainple is' nost likely to take place at the middle- In the exampleillustrated the bars ll'COnSiSt'O'l extensions of the connecting bolts12 of the two flanges. The arrangement shown in Figs. 18 and 19 differsfrom tlie fo 'egoing construction only in that. solid bars of anydesired cross section and of cast ironare used.

In the construction according to Figs. 16 to 19 the hoopingv of theconcrete is shown in the form of helical windingson the Considere systemIwhich is of advantage in such cases. As moreover the cross section ofthe 1 core and that ofthe concrete envelope-may have of great thickness,the transverse reinforcegment cannot be arranged.- as in the foregoingexamples, but the spacing 5 of. the

SfllCl transverse reinforcement must be equal to the meanbetweentheleast thickness-and the greatest thicknessaofjthe. concrete, eiivelopemeasured from the feore to thetrans-= w verse reinforcement. .It isunderstood that the form of the cross section. of

be diffei'ent'frorn that of the cross section of-the core.

r The rational. applicationofthese methods of constructing compressionmembers for bridges will be evident from the foregoing description.

T also intended tobe applied in cases'of com-j bined stress, for examplepush and pull, that The improved compression members are bars,- whilebetween flanges are screwed together by bolts- 12. The transversereinforcement 2 is' shown heavier fora determined distance tension.

nected lengths.

different profiles in some cases and .GSPQ. cially when-the hoopedconcrete envelope s 'forcement 1 in; any mani' erv stiffnessof the,skeleton,v the coremay concrete envelope, the hooping o't the concretehowever v conforming as closely as possible to the mentlas on theleft'hand handisideof 20.' ,inay also .be surrounded by helical wirecoils. arrangedat a givenidistancetherefrom, as 7 shown atrthedeft inFig. 2O and their purpose is to support the;tension inember'v at the isin cases of bending. For this purpose the member of solid bars or tubesof tubular cast ironbars, a wrought iron hooping surround ng them at agiven distance, and an ntermediate filling of co ncrete, is utilized.

only in the compression flange or in the struts of the structure Whilein the tension flange or part of the structuresubjected to the tension,the usual tension members of wrought iron or mild steel are used. If itis intended, that this reinforcement should constitute a resistiveskeleton even without the concrete envelope in order to relieve the coreand to render the same .wholly or partly dispensable,.. the saidreinforcement members must be mutually connected. This is generally doneat the ends oftliejlreinforcing the same, projections or extensions, ofthe compression, flange reinforcement extend into the tension flange andsupport the tension bars. Further, itis also possible toeinbed the wholeiron reinforcement in a hooped concrete envelope in order to stillfurther increase the strength of the structure element. p s

The tension bars,,o r the whole of the ironskeletonmay if desired begiven an nitial Examples of the structure element intended for resistingpush and pull stressfare shownfin the form 'of girders with solid. web,o nted girders, such as 'trussed ,or

square girders.

Fig. 20 is an elevation and Fig.221 across section onthe line. G G of agirderfresting on two supports and having in its compression flangeasolid barl of cast iron of suitable cross section andlin oneor'se'veral con- This solid bar is provided at a suitable distancetherefrom with awinding 2' or with embracing straps; of Wrought iron ormild steel. In the bottom f flange of this .beam there is usual ftensionreinforcement 18, which in order to make resistive skeleton the, 7 Wholereinforcement without the presence of the ooiicretegfillin'gand envelopeand'there- V byi elieve the core from stress andrenderit: Y

partially, oriwholly dispensable, is connected at its ends 19 1 with thecompression reinmeans offbolts 21. 'Iolobtain: the necessary tend from;the core Tl of'the. compression reinforcement to; the tension flangewhich mayf eitherbe in. onejpiece with. the" reinforce s e ffs-.2 or maybe connected thereto .as .onthe, right These projections provided the Yforlexample by projections .20 em points of bending: Inthismanner thetwo portion of the girder structure tial tension as required. For thislatter purpose it is only necessary to screw up the nuts 21 at the endsof the tension member.

With this construction it is also possible to surround the compressionand tension flanges as a whole with a hooping arranged at a givendistance therefrom, and either consisting of a helical wire winding, orwith straps 22 to increase girder by resisting radial stresses. Thehooping surrounding the cast iron and also that common to all thereinforcements may be an iron network of any suitable arrangement inwhich the tensile strength of the wire is rationally availed of; in theexamples illustrated the longitudinal bars may be omitted. The networkmust be of such dimensions and of Such size of mesh that all the radialstresses arising within the cast iron core are with absolute certainty,transmitted to the hooping, which resists them. The concrete fills adouble function. Its main purpose is to make the effect of the hoopingeffective over the whole periphery of the cast iron. Under conditions,with suitable strength and thickness of the hooping iron, it is thuspossible to reduce the distance between the windings and the cores to aminimum; In the second place the compressive effect of the hoopedconcrete obviously comes into consideration only where there is asuflicient thickness of concrete. The provision of longitudinal bars, inthe hooping is recommended at the places of connection of the cast ironcore, where such bars strengthen the connections of the component parts.i

Figs. 22 and 23 show as further example a in elevation and in crosssection on the line H-H, in which the two flanges are connected to eachother in known manner by means of compression and tension members.pression member 23'consists in the cast iron ore 1 surrounded in thehereinbefore described manner by helical wire hooping 2, arranged at agiven distance from said core, and an interposed filling of concrete forthe transmission of the stresses. The tension flange 24 contains theusual tension bars 18 which are held'together by straps 25 spaced atsuitable distances. The connection of the two reinforcements 1 and 18 isprovided also in this case for the purpose of creatmg a self supportingskeleton without the concrete envelope, and which may if desired begiven initial "tension.

Fig. 21 illustrates a girder attached to a column 26, that is with builtin ends, whereby positive and negative moments are present, inconsequence of which the compression reinforcement 1 goes at the columnfrom the top flange to the bottom flange, and the the strength of theThe com tension reinforcement 18, on the contrary, from the bottomflange to the top flange.

In Figs. '25 and 26 there is illustrated in elevation and cross sectionon I-I a beam in which the cast iron compression reinforcement 1 isitself a trussed structure, while the tension reinforcement 18, as inFig. 20 attached to the bottom of the structure, is anchored at the endsof the same in such a manner that the tension member may be tensioned inorder to impart an initial tension to the skeleton. Two wedges 27 asshown in Figs. 25 and 27 (a section on K K), may be used for thispurpose, the wedge being semi-circular form whereby the end of thetension bar may be passed round the same and formed in a loop 28. Toprevent slacking of the loop a wedge 31 is fitted withinthe same whichis either effective only at the binding 32, or is of such length that itabuts against the same at one end and against a block at the other end.The two wedges are connected by means of a bolt 29 and can be movedtowards or away from each other along inclined surfaces 33 transverselyto the girder for the purpose of tensioning or slackening the tensionbars. In

the example illustrated these inclined surfaces are located on lateralprojections 30 on the core or compression reinforcement, but they may beon the core itself. In this case also the compression and tensionreinforcement as a whole is surrounded by a hooping 22 keeping bothparts in fixed position relatively to each other. There is also providedthe concrete, for the purpose above described.

Having now described my invention, what I claim as new and desire tosecure by Letters Patent is:

1. In a girder, the combination with a tension flange, of a compressionflange in which a cast iron core is surrounded at a given distance by awrought iron hooping of sufficient tensile strength as to resist thebulging of the core under compressive strains, and the space between thecore and the hooping filled with concrete.

2. In a girder, the combination with a tension flange, of a compressionflange in which a cast iron core is surrounded at a given dis-. tance bya wrought iron hooping of sufficient tensile strength as to resist thebulging of the core under compressive strains, and the space between thecore and the hooping is filled with concrete, and of a wrought ironhooping surrounding both flanges and filled with concrete.

3. In a girder, the combination with a tension flange, in whichtension'bars are embedded in concrete, of a compression flange in whicha cast iron core is surrounded at a given distance by a wrought ironhooplng of suflicient tensile strength as to resist the bulging of thecore under compressive strains, and the space between the core and thehooping is filled with concrete, of ad-. justable connections betweenthe ends of the tension bars and the ends of the cast iron core, andabutments for the tension bars projecting from the castiron core. 7

' 5. In a girder, the combination with aten sion flange having tensionbars embedded in concrete, of a compression flange in which a castironcore is surrounded at a given distance by a wrought iron hooping ofsufiicient tensile strength as to resist the bulging of the core undercompressive strains, and,

the space between the core and the'hooping is filled with concrete, ofwedges adjustable across the ends of theoast iron core and'hav- 1 ingthe ends of the tension them.

bars secured to 6. In a structure member, a compression flange,consisting of a core piece .of brittle H material of high compressivestrength ern-v bedded in an envelope of hooped concrete,

a tension flange consisting of tension bars exterior to said hoopedconcrete, wedges at' the end of the'core piece transverse to the same,inclined surfaces on the core piece with which the said wedgesco-operate,'and:

means for attaching the ends of thetension members to the "wedgeswhereby initial ,ten-' sion may be given the said members.

In-testimony whereof Lhave signed my name to this specification in thepresence of l two subscribing witnesses.

Witnesses;

KVARLVREHAK, c AUGUST F UGGER..

Dr.FR lTZ EDLER'vOn M ER ER, j

